Page 22 – Resist Temptation – Equilibrillate!
It
is all too easy to look at the scatter of data points on the
chart,
and
edit out the ones you don’t like!!
No!
Do not “doctor” the data.
”Never,
never, never” – to quote the Reverend Doctor Ian
Paisley
(But
I don’t think he was talking about scientific honesty)
All
these data points are real. They are measurements of what actually
happened.
The
whole point of taking measurements is to quantify and understand
what is happening.
So,
those points describe something that is going on. Find out
what.
Plotting
the same data against time, it becomes very clear.
It
takes time for the engine to warm up!
To
reach thermal equilibrium.
There
is no point in trying to draw a power curve UNTIL the engine has
reached steady state.
Yes,
it can be as long as 30 minutes.
It
varies with how much metal there is in the engine and how strong,
or weak, the burner is.
When
starting a Stirling it is essential to prevent the engine from
over revving.
The
technique is, as the revs start to rise, to slowly increase the
load.
And
keep the revs relatively steady
Take
readings as you go, say every minute. When the revs no longer rise
and you get
three
readings the same, the engine is now ready to start measuring the
power curve.
But
charting the data for only the first 30 minutes - see what
happened.
The
line on the chart shows the time sequence. The engine started,
bottom left
on
the chart and progressed, zig-zag fashion, upwards as time,
progresses.
